With the exception of creatures with perfect maneuverability, I never understood why flying creatures can't be tripped. I envision tripping a flying creature where the tripper would grab or using a weapon to hook onto the flying creature's leg or wing and yank them down to the ground. If one fails the trip check bad enough that'll be trip themselves it could be the fact the attempt just knocks them off balanced and they fall down to the ground as result.

Sure "tripping" the flying creature by yanking them down would be more difficult than sweeping their legs from under than them. But is it really so impossible that it can't be done, not even four or six legged creature are immune.

I didn't know that existed. But after reading it on the PFSRD, I find that's another silly maneuver, I don't understand why they can't force a move into the wall or fire. Besides without the prone condition it's like you cause them to simply just land rather then forcing them crash to the ground.

So what if someone who flew by means of magic (actually, it could even be Levitate, I think), is prone, in that condition by whatever means, and wants to fly up? Do they need to spend a move to stand up, then fly? Or, can they fly up, then spend a move to stand up (thus having the prone condition while being floating in midair)? Do they even need to spend the action at all, or does flying away from the ground remove the prone condition automatically?

I've always treated it like Stalling or failing to maintain minimum forward movement was done in 3.5.

3.5SRD wrote:

If a flying creature fails to maintain its minimum forward speed, it must land at the end of its movement. If it is too high above the ground to land, it falls straight down, descending 150 feet in the first round of falling. If this distance brings it to the ground, it takes falling damage. If the fall doesn’t bring the creature to the ground, it must spend its next turn recovering from the stall. It must succeed on a DC 20 Reflex save to recover. Otherwise it falls another 300 feet. If it hits the ground, it takes falling damage. Otherwise, it has another chance to recover on its next turn.

I just replace the reflex save with a fly check and make it a move action rather than a full round.

I envision tripping a flying creature where the tripper would grab or using a weapon to hook onto the flying creature's leg or wing and yank them down to the ground.

That sounds more like a grapple.

To trip someone standing you could sweep their legs or use your weapon to hook onto their legs and pull them out from under them.

So, your explanation has changed, but you are leaving out one element. A trip maneuver is effective because once you remove the target's balance, gravity does it's part in bringing the target to the ground. A flying creature is able to counter gravity.

The only argument you could make for tripping a flying creature is that it may cause them to become unbalanced during their flight, but it's not worth it make a rule to account for that. If there was, the devs would have done so.

If you want to bring a flying creature to the ground with a CMB maneuver, performing a grapple & move, reposition, or a drag is the way to go.

I think there were rules for tripping flying creatures in 3.5. Not sure though, and if that's the case, I dunno why they didn't make it to Pathfinder.

I suppose it'd be a different effect that just shared its mechanics with the trip combat maneuver. Like, hurt it's wings or disrupt its flight somehow. It was just called "tripping" because it'd be too much of a niche scenario to warrant its own combat maneuver and apropriate feats.

In Pathfinder, the closest thing I can think off of the top of my head right now is the Gunslinger ability to force flying enemies to make Fly checks or fall 20ft.